The tmpfs filesystem was used to carve a 4Gbytes filesystem out of memory. This tmpfs filesystem, which keeps all files in virtual memory, was used for caching purposes.
$ mkdir -p /proxycache $ mount -F tmpfs -o size=5120m swap /proxycache
This creates a 5Gbytes filesystem in main memory. Although only 4Gbytes are actively used by the proxy server, a 5Gbytes filesystem provides some spare room.